Our long term objective is to develop a cell-based therapy for cataracts. In the case of the cataractous lens in adults, this approach offers the advantage, when compared with plastic prosthetic lenses, that the regenerated lens would be entirely natural in function and would accommodate normally. The regenerated organ would also be young in cellular terms and would therefore have extended function even in an environment, such as the diabetic patient, that favored the formation of cataracts. A cell-based therapy would also offer a unique advantage for the treatment of cataracts in newborns where conventional intraocular lens implantation is complicated by the rapid growth of the immature eye (a newborn's eye is 17 mm in length but grows to 22 mm by the end of the second year). [unreadable] [unreadable] The experimental strategy is to develop the techniques for production, identification and isolation of lens progenitor cells from mouse embryonic stem cells, and then to determine whether lens progenitors will form a lens in situ after implantation in the empty lens capsule of an experimental animal. Three Aims are designed to lead us towards this long-term goal. [unreadable] [unreadable] Aim 1 - to derive ES cell lines that give lens progenitor-GFP expression in chimeric mice. To prepare for the derivation on lens progenitor cells in culture, we will generate ES celt lines that give the normal Pax6 ectoderm enhancer expression pattern in chimeric mice. Aim 2 - To determine whether lens progenitor cells can be identified and isolated from embryonic stem cells. We will ask whether mouse embryonic stem cells are a source of lens progenitor cells using a variety of differentiation conditions in culture. Aim 3 - To determine whether lens progenitors will form a lens in situ. We will determine if lens progenitors isolated according to Aim 2 can generate a lens when placed in the empty lens capsule in nude (immune deficient) rats. If we are able to observe lens development from implanted progenitors, we will have established the basis of a cell-based therapy. Once established in animal models, the techniques described would be used with human ES cells and additional steps taken toward a practical therapy. [unreadable] [unreadable]